linux-kernel - Re: [PATCH] mm: Make mem_cgroup_id_get_many dependent on MMU and MEMCG

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Message-ID: <8c489836-b824-184e-7cfe-25e55ab73000@arm.com>
Date:   Thu, 5 Mar 2020 09:49:23 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm: Make mem_cgroup_id_get_many dependent on MMU and
 MEMCG_SWAP

Hi Michal,

On 3/4/20 4:53 PM, Michal Hocko wrote:
> On Wed 04-03-20 14:23:48, Vincenzo Frascino wrote:
>> mem_cgroup_id_get_many() is currently used only when MMU or MEMCG_SWAP
>> configuration options are enabled. Having them disabled triggers the
>> following warning at compile time:
>>
>> linux/mm/memcontrol.c:4797:13: warning: ‘mem_cgroup_id_get_many’ defined
>> but not used [-Wunused-function]
>>  static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned
>>  int n)
>>
>> Make mem_cgroup_id_get_many() dependent on MMU and MEMCG_SWAP to address
>> the issue.
> 
> A similar patch has been proposed recently
> http://lkml.kernel.org/r/87fthjh2ib.wl-kuninori.morimoto.gx@renesas.com.
> The conclusion was that the warning is not really worth adding code.
> 

Thank you for pointing this out, I was not aware of it. I understand that you
are against "#ifdeffery" in this case, but isn't it the case of adding at least
__maybe_unused? This would prevent people from reporting it over and over again
and you to have to push them back :) Let me know what do you think, in case I am
happy to change my patch accordingly.

[...]

-- 
Regards,
Vincenzo